Definition of drop-in in English:

adjective

Most of the time it is moored up as an informal drop-in restaurant for everything from a cyclist's brunch of French toast, bacon and maple syrup or pan-fried mushrooms on toast to a well-earned coffee and cake at the end of a walk.

To try to halt the explosion of cases, health bosses are organising drop-in sessions, school visits and extra GP surgeries to vaccinate teenagers and young people against the virus.